There’s really no exact answer I’m afraid. The “which bass should I buy” conundrum is a difficult one to answer and one that only you can I’m afraid.
Play as many basses as you can in stores and pick the one you like the look, feel and sound of most.
Anything by Yamaha is great. The BB series are particularly good at all price points. Sire, you can’t go wrong, they’re definitely the “in thing” at the moment in terms of value and quality….
….but honestly it’s endless. For 5/600 quid you can get a superb used bass, and as the years of playing bass go on, your taste and requirements will change, so something versatile is always good, personally I’d stick to 4 strings for now, and, re-sale value is worth thinking about too, because if you’re on here, it’s highly likely that you’ll get hooked on buying/selling/trading gear.
Good luck